Conventionally, various types of apparatus, which open and close electrically a trunk lid of a vehicle such as an automobile, have been suggested as examples as is disclosed in JP2002-201856A, JP2002-219937A and JP2002-242532A. FIGS. 5, 6 and 7 are side views illustrating an opening and closing mechanism 81 which is included in a trunk lid opening and closing apparatus. More particularly, FIG. 5 is a side view illustrating the opening and closing mechanism 81 under the circumstances that a trunk lid 87 is at a fully closed state. FIG. 6 is a side view illustrating the opening and closing mechanism 81 under the circumstances that the trunk lid 87 is opening or closing. FIG. 7 is a side view illustrating the opening and closing mechanism 81 under the circumstances that the trunk lid 87 is at a fully open state. Those opening and closing mechanisms 81 make a pair at both sides in a vehicle lateral direction. Here, FIGS. 5, 6, and 7 respectively illustrate the opening and closing mechanism 81 mounted at the right side as viewed from the rear, inside of the vehicle. The opening and closing mechanism 81 mounted at the left side possesses substantially the same structure as the right-side one, and the description thereof will be omitted herein.
As is apparent from FIGS. 5, 6 and 7, the opening and closing mechanism 81 incorporates, therein, a hinge arm 82, which is bent and exhibits an approximately U-shaped structure; a torsion bar link 83; a driving unit 84 configured with a motor having for example a speed reducer; a first link 85; and a second link 86.
One end portion 82a of the hinge arm 82 is freely rotatably supported by a body of a vehicle (referred to as a vehicle body) 80 via a shaft 91, while the other end portion 82b thereof extends outside through an opening portion 80a that is formed at a trim (a cover for an inside surface, a wall lining) and is positioned behind the shaft 91, i.e., at the right in FIG. 5. When the trunk lid 87 is at the fully closed state, as illustrated in FIG. 5, the other end portion 82b of the hinge arm 82 extends approximately horizontally towards the rear of the vehicle. The trunk lid 87 is securely mounted on the other end portion 82b of the hinge arm 82.
As for the torsion bar link 83, one end portion thereof is rotatably supported by the vehicle body 80, while the other end portion thereof is freely rotatably supported by the hinge arm 82 via a shaft 92. The torsion bar link 83 is configured to bias the hinge arm 82 counterclockwise in FIG. 5 and assists the trunk lid 87 to be opened.
The driving unit 84 is supported by the vehicle body 80, and, when it is supplied with an electric current, its output shaft 84a rotates clockwise or counterclockwise in FIG. 5. This output shaft 84a is positioned below the shaft 91. One end portion of the first link 85 is connected to the output shaft 84a so as to rotate integrally therewith.
The other end portion of the first link 85 is freely rotatably supported by one end portion of the second link 86 via a shaft 93. The other end portion of the second link 86 is freely rotatably supported by the hinge arm 82 via a shaft 94. The shaft 92 is positioned at an approximately intermediate portion between the shafts 91 and 94 on the hinge arm 82.
As described above, a four-link mechanism is configured with the hinge arm 82, the first link 85, the second link 86 and the vehicle body 80. Therefore, in response to an operation of the four-link mechanism implemented by activating the driving unit 84 (the output shaft 84a) to rotate, the hinge arm 82 is operated back and forth via the first and second links 85 and 86, and the trunk lid 87 provided at the other end portion 82b of the hinge arm 82 is opened and closed.
In the opening and closing mechanism 81 with the above-described structure, a reference L1 denotes a length from the output shaft 84a relative to a line of action l1 extending on the shafts 93 and 94, while a reference L2 denotes a length from the output shaft 91 relative to the line of action l1. In such circumstances, a relationship between a torque T1 about a pivot point of the shaft 91 of the hinge arm 82 and a torque T2 about a pivot point of the output shaft 84a is expressed by the following equation with a link ratio of L2/L1;T1=(L2/L1)·T2.Therefore, a torque T1 is increased when the hinge arm 82 is pushed at a portion that is distant from the shaft 91. However, in the perspective of improving the appearance of the trunk lid 87 or of the rear appearance of the vehicle, the joint position of the second link 86 to the hinge arm 82 (via the shaft 94) is determined so as not to outstand the second link 86 outside from the opening portion 80a of the trim even when the trunk lid 87 is at the fully open state (FIG. 7).
While the trunk lid 87 is being operated to open or close, the output shaft 84a is on occasions located on the straight-line l2 extending between the shaft 91 and the shaft 94. In such circumstances, an angle θ, which is formed by the first and second links 85 and 86 within an operation range of the trunk lid 87 to be opened or closed, reaches a minimum, and the link ratio of L2/L1 reaches a maximum. The torque T1 hence reaches a maximum. The angle θ is, in other words, formed by a straight-line l3 and the straight-line l1 both diverging from the shaft 93. The straight-line l3 connects the shaft 93 to the output shaft 84a. Meanwhile, because a degree of force, which is required to operate the trunk lid 87, reaches a maximum when the trunk lid 87 is to be completely closed, the output shaft 84a is positioned within a space where the output shaft 84a can be mounted, so as to be closest to the straight-line 12 extending between the shafts 91 and 94 when the trunk lid 87 is at the fully closed state as illustrated in FIG. 5. FIG. 5 illustrates an angle θ1 formed by the first and second links 85 and 86 when the trunk lid 87 is at the fully closed state.
Further, in order to block the torsion bar link 83 and the second link 86 from interfering with each other, the lengths of the first and second links 85 and 86 are determined in such a manner that the first link 85 measures a predetermined length or more.
Furthermore, the link ratio of L2/L1 is increased in response to decrease in the angle θ formed by the first and second links 85 and 86. The torque T1 is hence increased. However, in order to avoid turnover (a reversal of a force acting direction) of the first and second links 85 and 86 due to dimensional differences, deflections due to high-load applied thereto, and so on it is preferable that the minimum angle θ2 (FIG. 6) which is formed by the first and second links 85 and 86 within the operation range, be 30 degrees or greater than that.
Likewise, in order to avoid turnover (a reversal of a force acting direction) of the first and second links 85 and 86 due to dimensional differences, deflections due to high-load applied thereto, and so on it is preferable that the maximum angle θ3 (FIG. 7) which is formed by the first and second links 85 and 86 within the operation range, be 140 degrees or less than that.
Depending on types of vehicles, in evaluating the positions of these members by the above-described modes, as far as the known hinge arm 82 is employed, the minimum angle θ2, which is formed by the first and second links 85 and 86, may not on occasions be able to be controlled at 30 degrees or greater than that. In this case, although the minimum angle θ2 can be increased with the first link 85 shortened for example, it may result in interference between the torsion bar link 83 and the second link 86.
As an alternative, if the position of the shaft 94 is shifted to the side of a tip end of the hinge arm 82 (i.e., to the side of the other tip end 82b), the minimum angle θ2 can be increased. However, when the trunk lid 87 is completely opened or is maintained at the fully open state, it may cause the second link 86 to appear outside through the opening portion 80a of the trim, which may undesirably damage the appearance of the trunk lid 87 or the rear appearance of the vehicle.
As another alternative, if the speed reduction ratio of the driving unit 84 is lowered with a reduced outer diameter of a gear 84b, the minimum angle θ2 can be increased by shifting the position of the output shaft 84a upward (upward in FIG. 6) at a shifting amount corresponding to the reduced amount of the outer diameter of the gear 84b. However, in this case, the output of the driving unit 84 is lowered.
In order to assure the minimum angle θ2 at 30 degrees or more, sill another alternative would be to develop or newly create a hinge arm, which possess a different shape in substitution for the known hinge arm 82. However, because this may cause an extra load for a design change and may reduce a versatility of components, this idea is less realistic.
The present invention has been made in view of the above circumstances, and provides an opening and closing apparatus for a vehicle trunk lid, the apparatus which can at least open or close a trunk lid by using a known hinge arm, can reduce a load of design change and can assure the minimum angle formed by first and second links at an appropriate degree.